The present invention relates to a vent valve for a thermostatic valve of a coolant circuit of an internal combustion engine, with a cage made of one piece of metal, and a ball serving as the sealing element. The cage has a pot-shaped part with an inside diameter larger than the diameter of the ball. The bottom of the part is provided with a vent opening surrounded by an outwardly projecting neck, whose edge is abutted by retaining means retaining the ball with play.
U.S. Pat. No. 4,059,881 shows a vent valve of the above-described general type in which the pot-shaped fitting has a height roughly corresponding to the diameter of the ball. The edge of the pot-shaped insert whose inside diameter is approximately twice the diameter of the ball is abutted by an initially axially directed tab which is later bent inward at a distance from the bottom of the pot-shaped part which roughly corresponds to one and one-half times the diameter of the ball. It is not disclosed in U.S. Pat. No. 4,059,881 how the cage is made. However it can be assumed that the cage is made from a section of tubing constructed in the vicinity of the neck or expanded in the area of the pot-shaped part.
It is also known from German Patent DE 81 02 817.2 U1 that a one-piece cage can be manufactured by machining. The pot-shaped part of this cage has a height which is more than twice the diameter of the ball. After the ball is inserted, the edge of the pot-shaped part is pressed inward so that an opening remains whose diameter is less than the diameter of the ball. In addition, the cylindrical walls of the pot-shaped part are provided with transverse bores.
Vent valves of the initially described general type are used in large numbers. An object of the present invention is to provide a vent valve of the general type whose manufacture allows mass production at low cost.
This and other objects are achieved by the present invention by making the cage in one piece from an originally flat metal sheet by stamping, deep-drawing, and pressing, with a pot-shaped part with a height roughly corresponding to the radius of the ball, and with an edge abutted by a plurality of tabs uniformly distributed in the axial direction of the pot-shaped part and provided with inwardly bent ends, the length of which corresponds at least to the height of the pot-shaped part.
The tabs which are later bent and raised make it possible to hold the cage securely in tools during manufacture of the pot-shaped part and the neck so that the entire cage can be manufactured in simple fashion by stamping, deep-drawing, and pressing.
In certain embodiments of the invention, the transition between the bottom of the pot-shaped part and the neck is in the form of a frustroconical valve surface. This valve surface, which ensures the necessary tightness, can be produced in simple fashion by a pressing process, this process being combined with another work step.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.